The invention relates to an electromagnetic drive device, more especially for a valve, comprising an electromagnet having a magnetizable core with a plurality of limbs and an energizable winding arrangement surrounding at least one limb of the core, said device further comprising a magnetizable magnet armature able to be moved in relation to the core by varying the winding arrangement current.
Such an electromagnetic drive device is for example disclosed in the British patent publication 2,289,572 A, the core and the magnet armature constituting a so-called EI arrangement and the winding arrangement being constituted by a winding surrounding the middle limb of the E shaped core.
Starting with such a device one object of the invention is to provide an electromagnetic drive device, which renders possible more rapid switching while having a simple structure.
In accordance with the invention this object is to be fulfilled by the core having at least one U arrangement and preferably being formed as a U core or even as an E core and essentially by a plurality of sheet metal elements resting against each other and extending athwart the direction of the parallel limbs, the parallel limbs being respectively surrounded by one winding of the winding arrangement.
Owing to this particular arrangement high energy densities are produced in the magnetic field of the electromagnet. Owing to such high energy density there is the possibility of achieving rapid switching movements of the magnet armature, that is to say short switching times. Owing to low losses the drive device of the invention achieves a high efficiency.
Advantageous further developments of the invention will appear from the dependent claims.
Since the windings of the winding arrangement can be connected in series or in parallel to one another, it is possible for the overall resistance of the winding arrangement to be varied.
It is an advantage for the sheet metal elements constituting the core to possess a U or an E configuration. This renders possible simple manufacture of the core by superjacent stacking of the individual sheet metal elements.
It is furthermore convenient for the cross section of the core and/or of the magnet armature to have a polygonal and more particularly rectangular outline. For manufacture of a laminated core identical sheet metal elements are employed so that the core may be produced at a low cost.
As an alternative to this the cross section of the core and/or of the magnet armature may be oval or circular. More particularly, a circular cross section of the core may allow an adaptation of the form to the frequently circularly cylindrically wound windings.
It is also an advantage for the core and/or the magnet armature to consist of low retentivity magnetic material. Owing to this feature an low coercive field strength is ensured.
In the case of such low retentivity magnetic material it may be a question of ferrimagnetic or, respectively, ferromagnetic material. A ferrimagnetic material has a high resistivity. As a ferrimagnetic material iron may for example come into question.
Moreover it is expedient for the windings respectively to possess a non-magnetizable winding carrier, on which the winding is mounted. It is in this manner that a gap filled with the winding carrier is produced between the windings and the respectively associated limb of the core.
In the case of this design the winding carrier may consist of plastic so that extremely economic manufacture is possible.
The electromagnetic drive device in accordance with the invention will now be described in detail with reference to the accompanying drawings.